1. Field of the Invention
The present invention generally pertains to internal combustion engine cooling arrangements and, more particularly, to water jackets for multi-cylinder internal combustion engines.
2. Description of Related Art
Consistent and even cooling is necessary for proper operation of an internal combustion engine. More specifically, if the engine cylinder temperature is too high, the fuel will prematurely reach ignition temperature during the compression stroke. This undesirable phenomenon is known as auto-ignition or xe2x80x9cknockxe2x80x9d, and creates inefficiencies in the engine operation. Accordingly, it is desirable to cool the cylinders and the cylinder head. However, cooling the cylinder head, especially the portions overlying the cylinders, is particularly troublesome because these areas are crowded with components and also because these areas experience particularly high heating. Moreover, cooling of the cylinder head at the area between adjacent cylinders is also problematic due to heat build up in this area.
The cylinder head typically defines a water jacket passageway through which cooling liquid flows. Due to the configuration of the water jacket passageway, especially the irregular enlargements that are created in the passageway portions overlying the xe2x80x9csiamese areaxe2x80x9d between adjacent cylinders, there is a tendency for stagnation in the water flow, reducing the effectiveness of the cooling liquid at the areas that need cooled the most. Accordingly, areas of the cylinder head become overheated. Such localized overheating or inconsistent cooling of the cylinder head may lead to auto-ignition or knock. In response to this need, as shown by U.S. Pat. No. 4,690,104 and Japanese Laid-Open Application No. 56-148647, it has been proposed to constrict the water jacket passageway at the siamese area, thereby increasing the water velocity in the passageway at this area.
U.S. Pat. No. 5,799,627 discloses another attempt to provide more consistent cooling of the cylinder head. The ""627 patent introduces trapezoid-shaped projections that extend downwardly from the top wall of the head. The projections are disposed relatively above each cylinder and in a plane extending essentially normal to the cooling fluid flow direction and constrict the cooling passageway at that area.
Other patents, such as U.S. Pat. Nos. 4,553,505; 4,889,079; and 5,086,733 teach ribs that extend upwardly into the cooling passageway from the bottom wall of the cylinder head.
Also, some of the structures known in the art are very large and heavy, to the detriment of weight and fuel efficiency. Others of the structures are not configured to optimize the flow characteristics of the coolant passageway. Accordingly, there exists a need in the art for a cylinder head having a light-weight and a configuration to ensure cooling thereof. There also exists a need in the art for a flow control device in the water jacket passageway that will assist cooling the cylinder head at the areas between adjacent cylinders and at the areas at both ends of the cylinder head.
In accordance with the present invention, an engine includes an engine block defining a plurality of cylinders and a cylinder head disposed on the engine block. The cylinder head includes first and second ends, as well as upper and lower walls that cooperate to define a water jacket passageway through which coolant flows from the first end of the cylinder head toward the second end of the cylinder head. The lower wall is disposed on the block so as to overlie or cover the plurality of cylinders. One of the cylinders is near the first end of the cylinder head and another of the cylinders is near the second end of the cylinder head. The lower wall has at least one prominence associated with each cylinder such that the lower wall adjacent each cylinder is relatively recessed as compared to the lower wall directly over the cylinders.
In accordance with one aspect of the present invention, a plurality of ribs extend downwardly from the upper wall toward the lower wall. The ribs are designed to enhance the transfer of heat to the coolant fluid from the head lower wall. At least one of the ribs is disposed between the first end of the cylinder head and a cylinder closest to the cylinder head first end. Another of the ribs is disposed between the second end of the cylinder head and a cylinder closest to the cylinder head second end.
In accordance with another aspect of the invention, a plurality of ribs are disposed in the water jacket passageway relatively between adjacent cylinders. The plurality of ribs have a first end and a second end. The ribs are connected to one another at their first ends and are spaced apart from one another at their second ends.
In further accordance with another aspect of the present invention, the ribs extending downwardly from the top wall between adjacent cylinders have a lower edge facing the lower wall. The lower edges of the ribs are spaced a predetermined, generally equal, distance from the lower wall.